Addressing both interior and exterior lighting, this credit seeks to reduce light pollution that can block our view of the night sky and cause human health problems as well as ecological problems for many birds, insects, and other animals. Light pollution often represents nighttime lighting that isn’t needed, wasting energy while causing light trespass and contrast, reducing visibility.
Many people think that more lighting means better nighttime safety and security. However, too much exterior lighting can make outdoor and parking areas less safe by creating high contrast between lit and unlit spaces. Among other problems, when the human eye is flooded by bright light, it becomes harder to adjust to darker areas and shadows. Too much exterior lighting also means unnecessary energy consumption. Some objectives to keep in mind when striving for safe, efficient, and aesthetically pleasing lighting design are lighting uniformity, low contrast, no glare, and preventing light from spilling off the site. This can be achieved through judicious selection of fixtures with full cutoffA full cutoff luminaire has zero candela intensity at an angle of 90 degrees above the vertical axis (nadir or straight down) and at all angles greater than 90 degrees from straight down. Additionally, the candela per 1,000 lamp lumens does not numerically exceed 100 (10%) at an angle of 80 degrees above nadir. This applies to all lateral angles around the luminaire. that direct light toward the ground but prevent it from shining up into the night sky.
Full-cutoff luminaires reduce light pollution, improving views of the night sky.
This credit has four separate requirements, which can make compliance complicated—though not necessarily difficult. One addresses indoor lighting spilling to the outdoors, and three deal with exterior lighting, including façade lighting, site lighting of areas like pathways and parking lots. In most circumstances, these requirements are relatively easy and cost-neutral to meet. The biggest challenge often comes in dealing with light-trespass limits—light bleeding off the project site into a neighboring site—on projects with small or constrained sites. You will also need to attain low lighting power densities per ASHRAE 90.1-2007, which is a good general practice and won’t require you to compromise on aesthetics or cost.
You’ll need to pay careful attention to establishing a LEED project boundary, which plays an important part in meeting light trespass requirements. Involve an exterior lighting designer (or landscape architect) early in the design process to develop photometric plans and guide fixture selection during design.
Yes, as of 4/1/12 per LEED for Homes 2008 Interpretation #10147, “residential spaces (dwelling units only) within the scope of other LEED projects are also exempt from the interior lighting requirements.”
Yes, if they are within the LEED project boundary.
Yes, as long as the entire site meets the requirements.
No, hospitals are not exempt from the interior lighting requirements.
Significant reductions for tradable surfaces in LZ1 and LZ2 and some in LZ3. See the new table for details. It also added lighting power allowances according to light zones, removed a 5% adder, and introduced a base site allowance. Suggest revising response and adding a link to the Addendum i available for free download on ASHRAE website.
According to LI #10114, you can extend the lighting boundary to the centerline of the road.
According to the ASHRAE/IES interpretation of Standard 90.1, you can use the whole facade area. This is still a non-tradable allowance.
At grade level. A reviewer may request a 10’x10’ grid (5’x5’ for schools) on one side of the site from grade level to the height of the tallest light fixture.
No, per ASHRAE table 9.4.5, you can exclude lights in display windows, advertising, and directional signs as long as they are switched separately from other lighting.
If the canopy blocks 100% of the light then yes, but this is unlikely. Any light spillage needs to be counted toward the uplighting limit, but calculating this can be difficult. Using downlights is recommended instead.
Not currently, but USGBC is looking at exempting flag lighting from LEED v4 requirements.
According to LEED InterpretationLEED Interpretations are official answers to technical inquiries about implementing LEED on a project. They help people understand how their projects can meet LEED requirements and provide clarity on existing options. LEED Interpretations are to be used by any project certifying under an applicable rating system. All project teams are required to adhere to all LEED Interpretations posted before their registration date. This also applies to other addenda. Adherence to rulings posted after a project registers is optional, but strongly encouraged. LEED Interpretations are published in a searchable database at usgbc.org. #10236, street lighting that is required by the governmental authorities to be installed within the LEED project’s lighting boundary (whether existing or new) does not need to be included in any of the calculations.
All existing fixtures within the LEED project boundary would need to comply with the SSc8 requirements at the time the project is submitted for review. However, if the project elected to use the campus property boundary as the "lighting boundary" for SSc8 as allowed by LEED Interpretation #10236, existing fixtures within the lighting boundary, but outside the specific LEED project boundary would not have to comply with any of the SSc8 requirements. Essentially, the "lighting boundary" is only used in such circumstances for evaluating that the light trespass requirements are met at that boundary by lighting located within the LEED project boundary.
Advertising and directional signage, as explained in Addendum i of ASHRAE 90.1-2007, and further defined in the Users Manual for ASHRAE 90.1-2007, is exempt. Essentially, that means that internally illuminated advertising signs are exempt, but those illuminated by lighting that is not ‘integral’ to the signage itself must be included in the calculations.
Designate one responsible party to oversee exterior lighting-related LEED credit requirements. For large projects, this person may be the civil engineer or landscape architect. For small projects it may be the architect, lighting designer, or other relevant team member.
Identify the building owner’s goals for occupant safety and comfort as well as for architectural lighting, including façade lighting. Include these goals in the Owners Project Requirements for EAp1: Fundamental Commissioning.
One of the biggest barriers to reducing light pollution is the cultural and aesthetic affinity for brightly lit buildings. Owners can play an important leadership role in contending with these expectations, establishing aesthetic goals that do not include excess lighting for purely aesthetic purposes. The design team can play an important role by maintaining low levels of lighting and highlighting specific façade architectural features with focused, low intensity lights.
Projects that demand brightly lit facades and entrances, such as casinos, hotels, theatres and commercial complexes, may have a hard time reconciling these desires with the requirements of this credit. Deliberate lighting design can forge a compromise between the desire to emphasize the building facades and the need to eliminate light pollution in order to meet the credit requirements.
Identify the urban lighting zone as defined by IESNA RP-33, based on the population density of the neighborhood, in order to establish lighting requirements.
Finalize the LEED project boundary in coordination with other LEED credits. The responsible party and the project team should identify the lighting fixtures close to the boundary that will be part of the lighting trespass analysis.
Projects with a zero lot line may choose to use the curb as the LEED boundary for the purposes of documenting light trespass only, while using the site boundary for other credits. This is one of the few exceptions to the rule that the LEED boundary and corresponding site area be consistent across multiple credits. Sites that abut public rights of way may similarly use the curb to establish the site boundary for the purposes of LEED documentation. It can be challenging for projects with zero lot lines or with little open space to meet the maximum exterior illuminance requirement of 0.1 footcandles at the site boundary. Project teams are only responsible for lights that are part of their project. For example, municipal lights about which the project has no control do not need to be considered.
Campus projects can choose whether to comply with the requirements for the building site boundary or to meet the light trespass requirements for the campus as a whole. For a project on a campus, choosing to meet the light trespass requirements at the building level can be very difficult.
Identify local or regional lighting laws or required lighting levels for rights-of-way that may apply to the project site. These regulations may help teams identify areas to focus on when dealing with lighting trespass in the design.
Discuss fixture and lamp options with the landscape designer, civil engineer and other project team members, focusing on both reducing overall lighting power density, and on avoiding light trespass. Avoiding light fixtures that shine up into the sky is the easiest way to reduce light pollution and make better use of lighting. This can be done by eliminating exterior lighting entirely or by selecting “cut-off fixtures” with opaque covers that direct light downward.
Local or regional laws that regulate lighting levels typically do not require minimum input power in watts. Going beyond these local requirements by selecting energy-efficient fixtures can help your project meet codes for comfort and safety goals without compromising energy efficiency.
The credit requires a photometric study on site lighting that may add minor consultant costs but will add value by optimizing the design.
Optimizing lighting can eliminate unnecessary costs for extra lights and high-power fixtures.
Many smaller fixtures may make for a better layout than fewer high-wattage ones. The designer should be able to advise about additional infrastructure costs associated with an atypical lighting design. Low power density and light intensity may require higher first costs for fixtures that will save electricity costs during operations.
Rebates and incentives on the federal, state, and local levels are available for low-power and Energy Star lamps.
Safety concerns are not typically a valid excuse for higher exterior lighting allowances. Despite a perception of better safety with brighter lighting, floodlights can often create areas of deep shadow, and the high contrast can be difficult for the human eye to navigate. Use good design, downlights, and work with the owner to address any concerns.
Be aware of all requirements for interior lights so that fixtures do not direct light through windows to the outdoors. Identify locations where fixtures might have a direct line of sight to a window or other opening. The lighting designer should either eliminate those fixtures from the design, provide shades to prevent more than 10% of light from shining outdoors, or include controls to reduce the input power by 50% between 11 p.m. and 5 a.m.
Interior lighting cannot spill out of the windows after business hours, defined as 11 p.m. – 5 a.m. in the credit requirements. Window coverings or automatic controls like timers, occupancy sensors, or master switches have to shut off or reduce the input power by 50% for all non-emergency indoor lights during that time.
Fixtures that throw 50% or more of the cone of light out a window are likely to present problems.
To avoid letting this credit slip through the cracks, project owners or architects should ask the lighting designers at the outset of the project how they plan to achieve each aspect of the credit.
Additional light controls and automatic window screens may add to construction costs, but controls can reduce electricity consumption.
Identify the project location and IESNA-designated zone to determine the threshold for exterior lighting levels. Utilize resources like the website www.citydata.com to identify relevant population density and appropriate designation.
The lighting designer includes the design intent in Basis of Design for EAp1: Fundamental Commissioning, for all outside lighting requirements, listing minimum illuminance in footcandles, lumens, or candela for all spaces with controls, fixture requirements and design approach.
The lighting designer then develops the exterior lighting layout and selects fixtures that optimize light with low power use.
To determine the total power density for the project, the lighting designer tabulates all exterior space and identifies the wattage of selected fixtures to compare it with the LPD allowable by ASHRAE 90.1-2004, Exterior Lighting Section. The selected fixtures should have full shielding or cutoff to reduce light directed toward the night sky.
The lighting designer develops a photometric study for exterior lighting intensity, the impact of shades and cutoff fixtures, and light trespass from the project boundary. Use the photometric study to inform any changes in the design.
The key to achieving this credit is to find the optimum balance between lighting quality and lighting energy consumption. It is often assumed that more light is better, but a low level of uniform lighting throughout a site will eliminate the need to install bright halogen lamps that illuminate some areas and leave others dark in contrast.
Exterior lighting includes all ground lighting, all façade lighting, flag lighting, any rooftop or terrace lighting, and any other fixtures outside the building. Pay careful attention to exterior light fixtures and light levels at building entrances close to the LEED site boundary.
Revisit the LPD calculations to make sure any design changes maintain the threshold limits.
ASHRAE’s exterior lighting density table lists exterior spaces under two categories. Tradable surfaces are those where the average LPD of all those surfaces are within the total LPD limits. For example, in LZ4, both sales canopy lighting and stairway lighting have a maximum of 1.0 Watts/ft2. The project may decide to increase sales canopy lighting to 1.1 Watts/ft2 as long as the stairways compensate with a decreased LPD of 0.9 Watts/ft2 (given that the surfaces are the same area) so that the average of the two is 1.0 Watts/ft2. For non-tradable surfaces, such as bank ATMs, each space must individually comply with the ASHRAE requirements. Identify whether exterior surfaces are tradable in order to provide flexibility.
A photometric study will facilitate communication about lighting levels among the designer, owner and the design team. The study entails computer modeling simulating the lighting intensity of the designed layout in footcandles, lux or candela. It allows the designer to see the resulting output, with iterative design options as the fixtures are reduced or replaced. Typically the photometric study measures light levels in a 10’x10’ grid. The analysis also investigates the maximum initial illuminance value at horizontal and vertical limits on the site boundary to ensure they are within the limits of the project zone. If you find that lights are above the threshold, the designer may want to explore alternative numbers of fixtures and fixture types and present these alternatives to the owner, who makes the final decision.
Avoid aiming light at highly reflective site and ground surfaces, such as white pavement and water features, which can exacerbate light pollution. The photometric study may not capture these characteristics.
Some lighting manufacturers will offer to perform a photometric study of your site if your team selects their product for the project.
Security-oriented lighting designs such as those for prisons, parking lots, and walkways often focus too much on big, bright lamps. This can be counterproductive, creating high contrast between lit and unlit spaces, worsening visibility in both places. Use more moderate, uniform light levels for improved designs.
Some types of lighting are exempt from the ASHRAE limits on power density. Examples include advertisement signage, transportation signage, athletic fields, storage, and historic landmarks and other public monuments. Refer to Exceptions under ASHRAE 90.1 2004 Section 9.4.5.
The lighting intensity of conventional fixtures such as halogens, incandescents, and sodium halide lighting, drops off significantly after the first year of operation. LED or fluorescent fixtures will better maintain their lighting intensity at the level of the installation—contrary to the common perception that low power wattage fixtures, such as LEDs or fluorescents, have low lighting intensities.
Full cutoff fixtures can generally be specified at zero cost premium.
Cost premiums for this credit may come from the higher number of (shorter) poles and fixtures needed to achieve greater lighting uniformity.
New fixtures like LEDs with high lighting levels but low power density may cost more than conventional halogen fixtures, but most of the new fixtures have longer life and are less expensive to operate due to low electricity use and infrequent lamp replacement.
Costs for the photometric study can be decreased if manufactures agree to do their own calculations, which is common if you select their fixtures.
Come to an agreement among the owner, landscape designer and lighting designer about the appropriate lighting levels and site lighting distribution.
Demonstrate to the owner the project team’s decision about lighting levels for the final design. Owners may need to be shown similarly lit areas to understand the implications of a shift from a brightly lit façade and terrace.
Locally mandated lighting levels for exterior fixtures higher than LEED-mandated ASHRAE levels have been a stumbling block for credit compliance, but with proper documentation supported by a clear narrative, this challenge can be overcome. There is an option to not include those fixtures in the LPD calculations and light trespass requirement, but you must demonstrate that these fixtures are full cutoff. To document the credit, make the case that the legally mandated fixtures are beyond the control of the project. Demonstrate that the project has met the requirements with rest of the lighting. Provide a detailed photometric plan, the municipal regulations, and a narrative describing how the project has achieved all requirements of the credit except where the municipal regulations overrule it.
Confirm all the lighting fixtures are listed on the lighting plan. This ensures that the correct components are purchased and installed to maintain the credit requirements.
The designer reviews the final bid documents and budget estimates to confirm that the fixtures have not been substituted for by another type, and that interior lighting controls and window shades are not omitted.
If your team undertakes a value engineering process, make sure the full cutoff fixtures are not eliminated from the list or replaced by incandescent or high-powered halogen fixtures. These changes are often overlooked and may cost the project this credit.
If the project is going for multi-party contractor bid, make sure the bid’s package reflects the fixture specifications and performance. Otherwise the contractor may replace the specification with a similar lower-cost fixture that doesn’t have the same wattage or a cover for cutoff.
Full-cutoff luminaires should not cost more than conventional fixtures, but other common strategies for meeting this credit may add costs. These include controls, timers, sensors, and low-power lights like LEDs. Ensure that these features are not eliminated during value-engineering.
The designer should review shop drawings and visit the site for installation inspection. This ensures that the fixtures have a cut-off for uplighting, the ballasts are as specified, and the controls are all included.
The commissioning agent carries out the functional testing for all control sequences and timers if installed for lighting design.
Timer controls and automatic switches should be commissioned and inspected for performance periodically throughout their life to ensure they continue to serve the intent of the credit requirements.
The facility manager should be involved in the decision of whether to select light timers or automated blinds to comply with interior lighting requirements. Both solutions offer opportunities and challenges during building use, depending on how the building is used and occupied.
Long-life, low-power lamps like fluorescents and LEDs will help keep costs low for operations and maintenance.
Excerpted from LEED 2009 for New Construction and Major Renovations
To minimize light trespass from the building and site, reduce sky-glow to increase night sky access, improve nighttime visibility through glare reduction and reduce development impact from lighting on nocturnal environments.
Project teams must comply with one of the two options for interior lighting AND the requirement for exterior lighting.
Reduce the input power (by automatic device) of all nonemergency interior luminaires with a direct line of sight to any openings in the envelope (translucent or transparent) by at least 50% between 11 p.m. and 5 a.m. After-hours override may be provided by a manual or occupant-sensing device provided the override lasts no more than 30 minutes.
All openings in the envelope (translucent or transparent) with a direct line of sight to any nonemergency luminaires must have shieldingShielding is a nontechnical term that describes devices or techniques that are used as part of a luminaire or lamp to limit glare, light trespass, or sky glow. (controlled/closed by automatic device for a resultant transmittance of less than 10% between 11 p.m. and 5 a.m.).
Light areas only as required for safety and comfort. Exterior lighting power densities shall not exceed those specified in ANSI/ASHRAE/IESNA Standard 90.1-2007 with Addenda i for the documented lighting zone. Justification shall be provided for the selected lighting zone. Lighting controls for all exterior lighting shall comply with section 126.96.36.199 of ANSI/ASHRAE/IESNA Standard 90.1- 2007, without amendments1.
Classify the project under 1 of the following zones, as defined in IESNA RP-33, and follow all the requirements for that zone:
LZ1: Dark (developed areas within national parks, state parks, forest land and rural areas)
Design exterior lighting so that all site and building-mounted luminaires produce a maximum initial illuminance value no greater than 0.01 horizontal and vertical footcandlesVertical footcandles occur on a vertical surface. They can be added together arithmetically when more than 1 source provides light to the same surface. (0.1 horizontal and vertical luxMeasurement of lumens per square meter.) at the LEED project boundary and beyond. Document that 0% of the total initial designed fixture lumens (sum total of all fixtures on site) are emitted at an angle of 90 degrees or higher from nadir (straight down).
LZ2: Low (primarily residential zones, neighborhood business districts, light industrial areas with limited nighttime use and residential mixed-use areas)
Design exterior lighting so that all site and building-mounted luminaires produce a maximum initial illuminance value no greater than 0.10 horizontal and vertical footcandles (1.0 horizontal and vertical lux) at the LEED project boundary and no greater than 0.01 horizontal footcandlesHorizontal footcandles occur on a horizontal surface. They can be added together arithmetically when more than 1 source provides light to the same surface. (0.1 horizontal lux) 10 feet (3 meters) beyond the LEED project boundary. Document that no more than 2% of the total initial designed fixture lumens (sum total of all fixtures on site) are emitted at an angle of 90 degrees or higher from nadir (straight down).
LZ3: Medium (all other areas not included in LZ1, LZ2 or LZ4, such as commercial/ industrial, and high-density residential)
Design exterior lighting so that all site and building-mounted luminaires produce a maximum initial illuminance value no greater than 0.20 horizontal and vertical footcandles (2.0 horizontal and vertical lux) at the LEED project boundary and no greater than 0.01 horizontal footcandles (0.1 horizontal lux) 15 feet (4.5 meters) beyond the site. Document that no more than 5% of the total initial designed fixture lumens (sum total of all fixtures on site) are emitted at an angle of 90 degrees or higher from nadir (straight down).
LZ4: High2 (high-activity commercial districts in major metropolitan areas)
Design exterior lighting so that all site and building-mounted luminaires produce a maximum initial illuminance value no greater than 0.60 horizontal and vertical footcandles (6.5 horizontal and vertical lux) at the LEED project boundary and no greater than 0.01 horizontal footcandles (0.1 horizontal lux) 15 feet (4.5 meters) beyond the site. Document that no more than 10% of the total initial designed fixture lumens (sum total of all fixtures on site) are emitted at an angle of 90 degrees or higher from nadir (straight down).
LZ2, LZ3 and LZ4 - For LEED project boundaries that abut public rights-of-way, light trespass requirements may be met relative to the curb line instead of the LEED project boundary.
Illuminance generated from a single luminaire placed at the intersection of a private vehicular driveway and public roadway accessing the site is allowed to use the centerline of the public roadway as the LEED project boundary for a length of 2 times the driveway width centered at the centerline of the driveway.
You may use the LEED v4 version of this credit on v2009 projects. For more information check out this article.
Adopt site lighting criteria to maintain safe light levels while avoiding off-site lighting and night sky pollution. Minimize site lighting where possible, and use computer software to model the site lighting. Technologies to reduce light pollution include full cutoff luminaires, low-reflectance surfaces and low-angle spotlights.
This organization provides general exterior lighting design guidance.
Links to manufacturers with IDA-approved fixtures, information sheets and practical guides, and resources for learning.
This website is associated with the Lighting Research Center at Rensselaer Polytechnic.
SUPERLITE 2.0 is a lighting analysis program designed to accurately predict interior illuminance in complex building spaces due to daylight and electric lighting systems.
Lighting simulation software.
For someone who does not design lighting as their primary service, this free lighting calculation software can be downloaded here.
Elights sells full cut-off light fixtures.
A comprehensive source for understanding the lighting models underlying the commercial lighting power limits developed in ASHRAE/IESNA 90.1-2004.
This paper describes a method of measuring and predicting glow, glare and trespass in outdoor lighting.
This publication from the Illuminating Engineering Society defines urban lighting zones according to population density.
Perform calculations to demonstrate credit-compliance with exterior lighting power density requirements.
Refer to manufacturer cut sheets for the angle of light spilling above horizontal, the candela graph for maximum candela notation, and watts.
This graphic illustrates SSc8's particular rule for how the site boundary relative to illuminance can expand when a driveway meets a public roadway.
The schedule lists all the exterior fixtures that will be accounted for in the the lighting power density calculations required for this credit.
Provide documentation like this example to showcase the exterior lighting layout plan. You'll refer to this plan in providing fixture and photometric analysis.
This set of annoatated photometric plans was created by Bill Swanson, P.E. for LEEDuser as a teaching tool for SSc8 documentation issues. They are not intended as examples of actual documentation, though a lot can be learned from them. These documents include a detailed plan showing a compliant site with light levels in the site and as required around the boundary, with advice and useful tips. The fixture comparison document is a means to better understand and compare the spill light from different light fixtures and placements. Think of the purple line as the edge of a cutout with a pin thru the paper where the pole is. Move the cutout over the site when locating poles, if the cutout overlaps the line beyond the property line then that fixture cannot be located and aimed as placed. The driveway entrance example shows the impact of fixture placement around driveway entrances, and the special allowance for the site boundary around those entrances.
Sample LEED Online forms for all rating systems and versions are available on the USGBC website.
Documentation for this credit can be part of a Design Phase submittal.
The FAQs describes that the vertical footcandlesVertical footcandles occur on a vertical surface. They can be added together arithmetically when more than 1 source provides light to the same surface. needs to be measured at ground level.
In my opinion, it is not true.
Reference guide NC v3 describes that "Calculate the vertical light levels along and above the site boundary to a height of at least the highest luminaire on the site".
However, the problem is that the credit template does not require to submit vertical photometric analysis result. Then, what remain are 'do the project team have to prove that the project meets the light trespass requirement, and then how?'.
Therefore, I strongly suggest that the FAQs for vertical footcandles meaurement has to be revised as just reference guide describes.
Additionally, reference guide NC v4 might give us good example.
The FAQ is accurate. The full FAQ comment is, "At grade level. A reviewer may request a 10’x10’ grid (5’x5’ for schools) on one side of the site from grade level to the height of the tallest light fixture."
As you said, the credit template does not require a vertical photometric analysis. A reviewer doesn't always ask to see a vertical grid showing light levels. But since the Reference Guide mentions the vertical grid, the reviewers have asked to see it if they are concerned about a side of the property being too bright, as a way to verify compliance.
Absolutely, the project team needs to prove the project meets the light trespass requirements. The Reference Guide attempts to explain how to show compliance. Also, I have provided an example of how I show compliance on this website.
In my opinion, the Reference Guide should not be able to add requirements that don't exist in the credit language. But they do. And the FAQ is as accurate as I could make it. The vertical and horizontal light levels should be shown at grade level. And sometimes the reviewer will ask to see a vertical grid, because the Reference Guide says they can.
There are no good examples showing compliance in the Reference Guides. That's why I like this LEEDuser website. And reviewers have been known to ask for information not required. I'm offering the most accurate information I can.
We are working on a building including offices and a warehouse. For the warehouse, there is a night time operation assumed. For the interior lighting, the credit requirement / Option 1 states 'reduce by 50% the input power to interior luminaires with direct line of sight to envelope openings'. I would like to clarify how the direct line of sigth is defined - is it related as a) to the actual light source (i.e. bulb) within the luminaire, or b) to the whole luminaire? If a) is correct, would that be enough to specify downligth luminaires not allowing any direct view of the light source (bulb) from the exterior? I understand that reflected light would still be visible outside, but guess the intensity would be several orders of magnitude lower. Or is b) correct, in which case the use of downligth luminaires would make no difference? Thank you for any thoughts on this
It might be easier for you to follow the v4 version of this credit. There is no interior lighting requirements.
I have interpreted this as (b), the whole luminaire. The credit refers to the interior "luminaires" with a direct line of sight to envelope openings. It's very rare to have a bare lamp visible in any fixture.
Thanks Bill for your reply. Too late to swap to the v4, I will then take interpretation b) as applicable
We are working on a rural site which will be classified as LZ1, so will not be allowed any light to be emitted above 90 degrees from nadir. The way the SS Credit 8 is written within this version of LEED, it requires a “worst case” scenario of any adjustable exterior luminaires regarding the position of the light. (In other words any adjustable luminaires need to be directed to the sky, which would disqualify us from earning the credit.) The project's current design calls for tree mounted luminaires, which would be mounted to tree strap, as to not harm the tree.. The luminaire would be mounted in a fixed mounting position, and will not be adjustable to the owner.
Our specific question is whether or not LEED/GBCIThe Green Building Certification Institute (GBCI) manages Leadership in Energy and Environmental Design (LEED) building certification and professional accreditation processes. It was established in 2008 with support from the U.S. Green Building Council (USGBC). will interpret these tree mounted luminaires to be adjustable, or have any potential uplight contribution in our lighting calculations. Please advise.
The Reference Guide notes the adjustability of the fixture. Something with limited adjustability assumes the worst case. Something with full adjustability assumes 100% uplight.
I can't predict what the Reviewer will interpret. I would draw the line with how difficult is it to adjust. Can the fixture be adjusted using simple tools like a screwdriver or wrench? A tamperproof screw still has a screwdriver available that can change it. Or does the fixture or tree get damaged in order to adjust it?
At a minimum I'd allow at least some angle of change as the tree grows and the orientation may slip. But my guess is that 100% should be uplight since a strap can be undone by a contractor and reaimed later relatively easily.
I am working on a projects that consists of offices and a warehouse. For the offices, we would like to go via the option 1 (automated power reduction during out of business hours), for the warehouse we would like to use the option 2 (automatic shading), as the warehouse is 24hrs operation and has windows. I understand that it is possible to use a combination of Option 1 and 2, but I haven't found a way how to input the combination in the LEED Online form (it offers only EITHER Option 1 OR OPTION 2 path (including uploads).
Would the way forward be i.e. to provide uploads for Option 1, then switch to Option 2 and do a separate documentation upload?
Good question. I don't know. I'm sure others have faced this. I'd be curious how they did it and if the reviewer had any issues with it.
I'd suggest to pick Option #1 and submit everything together. On your plans you can show which areas are instead following Option #2. Provide documentation to support both conditions.
Jiri, did you find the way to submit both option in one template?
I suggest that first you have to choose option 1 or 2 and then you can use narrative description box in the template to explain your project's situation for another option. It will work. Thank you.
We are trying to determine how best to treat a pathway that extends beyond our LEED project boundary. The lighted pathway connects to the site of a future parking lot that will serve other (future) facilities. Approx. 1/10th of the lighted pathway is within our LEED project boundary, while 9/10ths of the path extends beyond the boundary as a long winding appendage that connects to the future lot.
The entire scope (current and future) is on the owner's property. As such, CIRCredit Interpretation Ruling. Used by design team members experiencing difficulties in the application of a LEED prerequisite or credit to a project. Typically, difficulties arise when specific issues are not directly addressed by LEED information/guide 10236 allows us to extend the "Lighting boundary" beyond the LEED project boundary. However, if we extend the lighting boundary to include this path, it raises the question of whether the path itself (and the associated grading) should be included in the initial LEED project boundary.
If grading for the path is necessary to install the lighting, then will we be expected to adjust the LEED project boundary to include this work, even though it's an appendage that serves the future parking lot?
No, the LEED Project Boundary does not move. The Lighting Boundary is completely independent of the LEED project boundary and is based on the Property Line, with modification. The Lighting Boundary is clearly defined within the LEED v4 credit language for this credit (see LEED Credit Library for v4). The LEED project Boundary is only relevant to this credit in one way. Only the exterior fixtures that are within the LEED Project Boundary "count" in your calculations. If they are outside the LEED Project Boundary they don't "exist" as far as the credit is concerned.
Of course this may also mean that any grading work that is specified and any new fixtures that are installed, on the part of the path that is outside the LEED project boundary, probably shouldn't be part of the LEED project and show up on your construction documents. You might have to set up a separate construction project with it's own drawings. But I'm not sure.
Also note that the LEED v4 version of this credit can be used on LEED 2008 projects. Check it out. It will probably make your compliance efforts easier,
The “ASHRAE 90.1.2007 with Addenda i” indicate that some lighting applications can be excluded : “Exceptions to 9.4.5:Lighting used for the following exterior applications is exempt when equipped with a control device that complies with the requirements of Section 188.8.131.52 and is independent of the control of the nonexempt lighting:
a specialized signal [...]
f. temporary lighting, ...”
I have two questions :
1. Are those exceptions just for the LPDLighting power density (LPD) is the amount of electric lighting, usually measured in watts per square foot, being used to illuminate a given space. calculation or for the illuminance calculation also ?
2. Can we consider that lighting only used for the maintenance of the roof, with an independent control device, is a temporary lighting and can be exclude from calculation ?
Thanks for your help
By "No" for the first answer, you mean that exceptions are only for the LPDLighting power density (LPD) is the amount of electric lighting, usually measured in watts per square foot, being used to illuminate a given space. calculation, is it right ?
Sorry, yes, that is what I mean. the exemptions are only part of 90.1, they have nothing to do directly with the light pollution credit.
If you are having trouble complying with the credit and you feel you have a good design, you should look at the LEED v4 version of the credit (which you can use on LEED-2009 projects)
I've been reading and re-reading the interpretations by USGBC and the posts on this site and I still feel like I can't positively state the answer to the following question our team has:
Can the LEED Boundary be different than the Lighting Boundary?
We have our LEED site boundary set at the property line. This boundary does not allow us to achieve SSc8. If we use the exception of half the drive for the lighting boundary, we then will achieve SSc8. We could change the boundary for all the credits but we've already submitted for the first round and don't want to go changing all of the documentation for all of the credits if we can just change the boundary for SSc8 and leave the rest as-is.
The Lighting Boundary and LEED Project Boundary are separate and pretty much unrelated. The Lighting Boundary is the Property line, modified.
Refer to LEED interpretationLEED Interpretations are official answers to technical inquiries about implementing LEED on a project. They help people understand how their projects can meet LEED requirements and provide clarity on existing options. LEED Interpretations are to be used by any project certifying under an applicable rating system. All project teams are required to adhere to all LEED Interpretations posted before their registration date. This also applies to other addenda. Adherence to rulings posted after a project registers is optional, but strongly encouraged. LEED Interpretations are published in a searchable database at usgbc.org. #10236 or better yet, the v4 version of this credit (you can use the v4 version on 2009 projects)
It says: 'The lighting boundary is located at the property lines of the property, or properties, that the LEED project occupies. The lighting boundary can be modified under the following conditions:
When the property line abuts a public area that includes, but is not limited to, a walkway, bikeway, plaza, or parking lot, the lighting boundary may be moved to 5 feet (1.5 meters) beyond the property line.
When the property line abuts a public street, alley, or transit corridor, the lighting boundary may be moved to the center line of that street, alley, or corridor.
When there are additional properties owned by the same entity that are contiguous to the property, or properties, that the LEED project is within and have the same or higher MLO lighting zone designation as the LEED project, the lighting boundary may be expanded to include those properties.
Thanks Glenn. I just wanted to make sure someone had successfully used this.
We have a permanent free standing canopy over all of the parking spaces on site. Would this fall under the canopy allowance for lighting power density calculations?
Under ASHRAE 2007 90.1, 9.4.5 allowances are:
Canopies and Overhangs - 1.25 W/sq ft
Uncovered Parking Areas - .15 W/ sq ft
Thanks in advance
I would count it as an interior parking garage with a LPDLighting power density (LPD) is the amount of electric lighting, usually measured in watts per square foot, being used to illuminate a given space. of 0.20 W/ sq. ft.
It is necessary to check the level of lighting in facades that are not in the limit of the project boundary? (This facades are in plazas inside the project boundary, but not in the limit)
I'm not sure how you are using the word "limit". Generally the project boundary is the same thing as the lighting boundary. But along roads we can use the centerline of the public road as the lighting boundary. Also, a campus can use a much larger lighting boundary than the project boundary.
If the light fixture or façade is within the project boundary it must be included in the calculations. There are some exceptions. It doesn't make sense to me when you say the facades are inside the project boundary, but not in the limit.
Hello Bill, I mean exterior walls but are not faced the street, but indoors. They aren't in line with the project boundary.
I understood that lighting pollution applies to light levels beyond the project boundary, caused by lights within project boundary, but not applies to interior facades. Is that true?
It sounds like the walls are blocking the light from the project boundary. They are still included but the walls and any other built structures are also included. The lights are there, you just can't see them from the project boundary.
Now if this is an open plaza there might still be uplight coming from these lights. That still needs to be included in your uplight calculation. And they still need to be counted in the lighting power calculations.
Thank's! I think I understand a little more.
We are developing a high rise multi-residential project (5 buildings) in a undeveloped land, the area is between the access to a national park and multiple neighborhood (residential units). The area belongs to a high priority zone established in municipal plans to increase density in this zone.
However the site falls into a "Zone1" by ASHRAE Addenda or "LZ-0" by MLO, but according to MLO "Selection of lighting zone or zones should be based not on existing conditions but rather on the type of lighting environments the jurisdiction seeks to achieve".
Can we use the last sentence from the MLO to change the ASHRAE Zone to a less rigorous one?? in addition to the Existent Municipal High-Priority Development Site definition.
First of all it depends on what version of the credit you are using. If you are using the 2009 version, then the MLO LZ definitions do not apply, only the ASHRAE/IES 90.1 definitions. The determination of the LZ for LEED is generally based on the project site itself, so I think you could justify an LZ2 designation according to 90.1 definitions based on your description of your project. You have a bit of an odd situation because you are up against national park land. If your GBCIThe Green Building Certification Institute (GBCI) manages Leadership in Energy and Environmental Design (LEED) building certification and professional accreditation processes. It was established in 2008 with support from the U.S. Green Building Council (USGBC). reviewer takes a conservative approach to LZ designation they might consider it to be LZ1. If you're are using the v4 version of the credit and the MLO definition, I think you'd be LZ1 or LZ2, certainly not LZ0.
I wonder how i should account a WAter fountain in the exterior of my building. It is like this one: http://www.hidroworks.com/galeria.php?id=2 . The are lamps in the base of the water fountain, so a level zero can be saw the luminosity, Should I account the lumes of this exterior ligthing in the Lamp Lumen1. A lumen is a unit of luminous flux equal to the light emitted in a unit solid angle by a uniform point source of 1 candle intensity.
2. A measurement of light output. Calculation (Table SSc8-4. Site Lumen Calculation)? or should i use a smaller value due to brigthess loos? or should i not account this lamp due to the fact that this ligthing system is an exterior ligthing system independent of the exterior ligthins system of the building?
I would count all of the light from the fountain as part of the uplight for the site.
There might be some brightness loss from round droplets reflecting light back towards the ground. It would be to difficult to calculate for a minor benefit.
You might be able to exclude the wattage for this lighting in the LPDLighting power density (LPD) is the amount of electric lighting, usually measured in watts per square foot, being used to illuminate a given space. calculation, if it is in an amusement park or public monument. Unfortunately this doesn't help at all with the uplight. There is nothing in the credit language that lets you exclude decorative lighting from the uplight calculation, even if it is controlled separately.
A project we are working on is considering including facade lighting with LEDs. The lighting on the facade is intended to take the form of a logotype associated with the client, so it is both facade lighting AND advertising signage. Can it therefore be excluded from the 90.1 calculations?
Sorry for the delay. Spring gets busy.
If it is internally illuminated signage, I would exclude it from the calculations. If the signage is decorative and shines on the façade, I would still consider it building signage that is excluded. Just make sure you explain the lighting is in the form of the company logo, and internally lit.
I have a question about the use of the LPDLighting power density (LPD) is the amount of electric lighting, usually measured in watts per square foot, being used to illuminate a given space. Calculation Template which we found here in the Documentation Toolkit.
We are working on a project with two entrance canopies which each cover a rather small area and have thus an "Actual LPD" which exceeds the "ASHRAE 90.1.2007 Allowable LPD". If we additionally want to use the base site allowance, where do we add the value to the table?
Or is it allowed to use a different/adjusted calculation table instead of the LPD Calculation Template?
Thank you in advance!
Tristan, I think your LPDLighting power density (LPD) is the amount of electric lighting, usually measured in watts per square foot, being used to illuminate a given space. Calculation Template needs to be updated with values from the new LPD table issued by USGBC.
Until then there is the sample credit form available on the USGBC website. I'm looking at version 4 of this form.
When you pick your LZ there should be a number that is shown in the box below. LZ3 will display 750 Watts. I wish it was automatically added to the table below but it's not. In Table SSc8-1 there are some blue boxes. These are what you can enter numbers into. The white boxes are automatically filled. On the right side of the table, 3 lines up from the bottom there is another empty blue box. The line says "ASHRAE Base Site Allowance used (Optional)" This is where you add the base site allowance.
Another qwerk I've noticed is the last line of the table will always say "No" unless you enter a "Lighting Location Description" into each line for the surface types above.
Let me know if this helps you or tell me more so I can try a different approach.
Thanks Bill! The sample credit form works perfectly. Since we have no non-tradable surfaces lit in the project, is it okay to just leave that table (Table SSc8-2) empty or should we set it to e.g. facades and enter 0 for the actual lighting power? (the function in the summary, to calculate the compliance seems to only work if everything is filled in)
The non-tradable surfaces table doesn't like being empty. Just enter a line, call it "None", select facades, area of 1, and 0 watts.
Okay great! Then we'll use that for the non-tradable surfaces. Thank you for the help!
in LZ3, no more than 5% of the total initial designed fixture lumens should be emitted at an angle of 90 degrees or higher from nadir (straight down). Do you think we can propose meeting this requirement by turning off part or all of the external lighting during night (eg. from 11pm to 5 am, same as for interior lighting), while not necessarily having cut-off luminaires. Any idea this could work?
You can propose anything, but this is not likely to be accepted. The interior and exterior requirements are separate, and it would be too easy to change the shutoff time for the exterior lights.
Thank you Bill for your quick response
We have a campus project which includes exterior lighting added within our scope and on our site to illuminate an adjacent private drive and an adjacent parking lot. (all campus properties). Neither drive nor parking are included in the LEED project boundary as they are existing and not used by occupants of our project. We will meet the interior escape, exterior uplighting and LPDLighting power density (LPD) is the amount of electric lighting, usually measured in watts per square foot, being used to illuminate a given space. requirements for this credit. The issue is the light trespass component. I understand the LEED lighting boundary can be extended as per CIRCredit Interpretation Ruling. Used by design team members experiencing difficulties in the application of a LEED prerequisite or credit to a project. Typically, difficulties arise when specific issues are not directly addressed by LEED information/guide 10236. However, extending this by 5 feet does not help us (lighting the street and parking is the goal) and documenting trespass around the entire campus boundary would be irrelevant and nearly impossible. So, my question is whether we can use the third provision of CIR 10236 to extend the lighting boundary to include just the parking and just the property across the drive as they are all campus lots. Or, would it be wiser, to make a case to omit this lighting from the site photometrics altogether as it is essentially meets the same intent as the exemption for municipal street lighting. (which is, of course, safety)
I'm not sure I understand your question, but I think you may be misunderstanding how the credit works with the Lighting Boundary. Trespass "measurements" are made at the Lighting Boundary, but only fixtures that are within the LEED Project Boundary have to be included in the calculations. So the parking lot and drive and any other contiguous properties owned by the school, of the same or higher LZ, can be combined and the Lighting Boundary moved out to the edge of these properties. If the boundary ends up a long long way from the LEED project boundary, then it pretty easy to say that you are going to have zero light from all the exterior fixtures within your LEED project site. You could just provide a map showing the lighting boundary, and not even bother with computer modelling. If some of the lighting boundary is close, then you can do the modelling. Or considier using the v4 version of the credit (which you are allowed to do on 2009 projects) and you can use the BUG method which does not require computer modelling.
The 5ft. offset you mention applies to Publicly owned hardscapeHardscape consists of the inanimate elements of the building landscaping. Examples include pavement, roadways, stone walls, concrete paths and sidewalks, and concrete, brick, and tile patios., and you say that everything is owned by the school. The lighting for the drive and parking could not be exempted unless it was specifically required by the government (which seems unlikely).
Are you referring to this text?
"-When there are additional properties owned by the same entity that are contiguous to the property, or properties, that the LEED project is within and have the same or higher lighting zone designation as the LEED project, the lighting boundary may be expanded to include those properties."
If the campus property is on either side of the street then the property is not contiguous. If the campus owns the street, then it is and the drive can be included within the lighting boundary.
You can only exempt the light from within your project boundary if the city is requiring this light. And then this needs to be proven in writing from the city's ordinance or some official communication from the city. Employees from my local city have told me that it is their responsibility alone to provide lighting on the streets they control.
We are working on a government facility which will potentially have Statues and/ or large War Relics displayed on-site. Could the lighting for these types of items be considered, "special feature area" which is referenced in the ASHRAE 90.1-2007 Table 9.4.5?
I think it would be fair to call it a special feature area.
Your bigger problem is going to be the uplight.
Bill, thanks for your input. Yes, there will most likely be uplighting around these features and I wanted to know if I had the option to "trade" this lighting, as a special feature, which is allowable per Table 9.4.5 in the ASHRAE handbook.
We have a project located on a military base where we are lighting a parking lot classified in an LZ3 zone. Our calculations show we are getting 0.01 vertical foot-candles in the parking lot across the road from our construction work area. The parking lot across the road is also part of the military base. Can the credit be achieved with a LEED boundary and the noted light levels being across the road in the other parking lot?
The LEED boundary is suppose to be at the centerline of the public road.
We are considering using some of up-lights to light some trees at night, I wonder if there is a way to calculate the lumens shielded by trees or by a canopy structure on top of it (very narrow spaced fins).
How to allow for that in the light spill evaluation?
LEED does not consider any vegetation to be a shield of lighting. All of the uplight will be counted as uplight.
A built canopy structure can be considered a shield but it is very difficult to calculate exactly how much uplight is blocked. You'll need a detailed analysis of the ies file to know how much light is emitted at each angle and then draw a sketch showing what angles are blocked by the canopy. The light that is not blocked gets counted as uplight. I've never found it to be worth the effort to figure this out.
A spill light evaluation I always use a lighting model. Ignore trees and other plants since they are not considered. If there is a wall along the perimeter of the project I will draw the solid wall in the lighting model which blocks some of the spill light. If there is a see thru fence I ignore that too because there is no way to estimate where a line of light will pass thru the fence and where it will be blocked.
Are you in LZ3 or LZ4 according to the lighting zone definitions used in the LEED v4 version of this credit? In LEED v4, landscape lighting is exempt from the uplight limits if you are in LZ3 or LZ4. You can use the v4 version of the credit on LEED-2009 projects
Hi Bill and Glenn,
The project is in LZ3, seems like LEED v4 for this credit is the only option for this project then, will have a look at it.
Be careful about the LZ definitions used in v4 which are from the Model Lighting Ordinance User Guide (MLO). The can be more stringent than the definitions used in LEED-2009. Projects that would qualify as LZ3 with LEED-2009 definition sometimes come out as LZ2 when using MLO definitions. It's your call to interpret the definitions and determine what LZ you are in, but make sure you have some defensible.
I cant seem to find any information about the lighting on driveways.
The only reference to roads I can find is under “uncovered parking areas, parking lots and "drives” which is 1.6 W/m2.
it would be great if someonce can inform me or confirm the matter
Driveways would fall under the category you referenced.
If your project was registered after November 2011 you're going to need to use the updated Table 1 for the lighting power allowances. (See link in the FAQ above) Drives were reduced and range from 0.4 to 1.3 W/m2.
I have a new student housing project on a large University campus. There is a cafeteria and student union inside of the new building. Across the street from the new building are all of the fraternity houses. As you can imagine these students are being encouraged to use the new facilities (cafeteria / student union) which are both open 24hours a day. With that being said, the University wants us to make sure the lighting on the street that separates the new building from the frat houses is adequate for safety reasons, which has pushed our allowable lighting power densities slightly beyond what is allowed on the street (which is not owned by the campus). Are there any allowances for slight deviations from the requirements based on safety reasons? The project complies with all other requirements set forth in the LEED guidelines. Thanks!
"... which has pushed our allowable lighting power densities slightly beyond what is allowed on the street (which is not owned by the campus)."
This sentence confused me.
Safety has rarely been allowed as an excuse to exceed light levels in the Credit. This situation will not be allowed a deviation.
Are you sure you are doing everything accurately. Have a second set of eyes in your office or on the design team that knows lighting try to show compliance.
Try another calculation option. There is one option for the v2009 credit and two options of the v4 credit. Sometimes if one doesn't work another one will.
Express to the City the need for additional lighting at this crossing.
I was still hoping for an answer to the following regarding Automatic Shading Devices:
This credit asks for uploads of product specifications, location plan, and riser diagram for automatic shading devices. Due to budget constraints our project will not have any automatic shading. Is this something I can simply document in the narrative, or do we need to specify some type of manual shade (ie: blinds) for the contractor to install? Please advise - thank you!
I'm afraid normal blinds would not be acceptable in order to comply to the credit requirements. There are other options to comply with interior lighting such as decreasing the lighting power during night hours.
You don't need to ask the same question multiple times. I have stated previously on this site, "Manual shades don't count as shieldingShielding is a nontechnical term that describes devices or techniques that are used as part of a luminaire or lamp to limit glare, light trespass, or sky glow. since they are not automatic and can be left open." The key word for interior lighting control is "automatic" in both option 1 and option 2.
Technical college campus has a road that runs along side my project. If the college owns the land on both sides of the road, does my lighting boundary stop at the centerline of the road or can I extend my lighting boundary across the road as the college owns both sides? Would it make any difference if the college "owned" the road in terms of be responsible for maintenance and snow removal?
If the college owned the road it would be considered part of the campus. If the government owns the road then it will need to comply with the centerline of road rules as we do with all public roads. I'll bet a lot of colleges have this issue.
You might be able to argue for an exception but the campus rules require a continuous property.
I just ran into this very situation on one of my own projects (although it is a commercial development not a campus.) Speaking as someone who had something to do with the creation of the Lighting Boundary concept, I can say that this situation probably wasn't considered when the definition was written. Conceptually, the Lighting Boundary should be able to "jump" across a public street when the property on the opposite side has same owner. The idea of putting the boundary at the centerline of the roadway was based on the assumption that a different property owner was on the opposite side of the street and that each of the two property owners (you and your neighbor across the street) get to "split" the public street. But if you are your own neighbor across the street, you effectively have contiguous properties by same owner that meet at the centerline of the street. That's my opinion. We should definitely get an official LEED interpretationLEED Interpretations are official answers to technical inquiries about implementing LEED on a project. They help people understand how their projects can meet LEED requirements and provide clarity on existing options. LEED Interpretations are to be used by any project certifying under an applicable rating system. All project teams are required to adhere to all LEED Interpretations posted before their registration date. This also applies to other addenda. Adherence to rulings posted after a project registers is optional, but strongly encouraged. LEED Interpretations are published in a searchable database at usgbc.org. on this. James, you may want to apply for special circumstances using my reasoning.
We submitted a Campus map that demonstrated our infill project is entirely surrounded by 2-5 layers of Campus properties. Nevertheless, the Reviewer appears to require a photometric site plan depicting the footcandle levels to the hundredths decimal place to demonstrate exactly where, within the Campus boundary, 0.01 footcandles occurs. Is it really necessary to spend even more money on this project documentation when the answer is so clear? Incidentally, project is in Flagstaff, AZ - home of THE strictest lighting code in the world. We designed with zero uplight and 2400-2700k. Astronomers at their local Observatory reviewed our lighting plans four times before approval. Lastly, are we required to prove that all roads on the campus are owned by the University?
I feel your pain. if the Lighting Boundary is a long long distance away from the project in all directions it would be obvious that there would be zero illumination at the Lighting Boundary from the project luminaires. So running the trespass calculation is pointless and unnecessary in my opinion. With that said, you must submit is drawing/map that shows the Lighting Boundary drawn clearly and with any notes you think should be there to explain how you determined the Lighting Boundary (such as identifying contiguous properties owned by the university and that they would be classified in same or higher LZ).
FYI, the Lighting Boundary is clearly defined in the LEED v4 version of this credit. It applies to the 2009 version of the credit via a credit interpretation #10236. You can also use the whole LEED v4 version of the credit on LEED-2009 projects and you might want to look at that. The v4 version is simpler to deal with and has compliance options that give you flexibility (no computer modelling required).
Your campus roads question is an interesting one and brings up an interpretation issue. If all the streets are private streets (not owned by the city) then you need to show that, and then you are all set with showing the lighting boundary out at the edge of the campus. If you have a public street along your project property line, and another university owned property across the street, then by definition the Lighting Boundary is at the centerline of the roadway. If you can't meet the trespass limits with the boundary at the roadway centerline then you could argue that the two properties are effectively continuous because their lighting boundaries are coincident. But a conservative interpretation would say that the property across the street could be sold in the future to another owner, so the Lighting Boundary has to stay at the center of the roadway.
Joyce. I've had the same problem lately with a small project inside of a much larger campus. To make the reviewer happy I extended the calculation grid until I got a 0.01 fc1. A footcandle (fc) is a measure of light falling on a given surface. One footcandle is defined as the quantity of light falling on a 1-square-foot area from a 1 candela light source at a distance of 1 foot (which equals 1 lumen per square foot). Footcandles can be measured both horizontally and vertically by a footcandle meter or light meter.
2. The non-metric measurement of lumens per square foot, one footcandle is the amount of light that is received one foot from a light source called a candela, which is based on the light output of a standardized candle. A common range for interior lighting is 10 to 100 footcandles, while exterior daytime levels can range from 100 to over 10,000 footcandles. Footcandles decrease with distance from the light source. The metric equivalent of a foot candle is 10.76 lux, or lumens per square meter. in each direction.
This credit used to be way too permissive. Now they seem to be looking for any detail to hold up the approval.
They've also been asking to verify the lights are not adjustable. I thought by submitting cutsheets of each light this would satisfy them. They don't seem to know if a light is adjustable just by looking at the cutsheets so the reviewer is asking me to state that yes indeed they are not adjustable. The next project I'm going to add a comment in each fixture description that it is "not adjustable".
Key considerations for this credit presented at Greenbuild 2009.
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